JP5903584B2 - Ultrasonic flow meter - Google Patents

Description

  The present invention particularly relates to an apparatus for measuring a flow velocity or a flow rate by ultrasonic waves.

  In the conventional ultrasonic flowmeter, as shown in FIG. 5, the ultrasonic sensor A2 and the ultrasonic sensor B3 are installed in the flow path 1 in the flow direction, and the control unit 4 starts the timer 5. At the same time, the drive circuit 6 is operated. First, the direction switching circuit 8 sets the ultrasonic sensor A2 to the transmission side and the ultrasonic sensor B3 to the reception side, and the ultrasonic waves transmitted from the ultrasonic sensor A2 driven by the drive circuit 6 are ultrasonic waves. The signal is received and detected by the reception detection circuit 7 received by the sensor B3 and receiving the output of the ultrasonic sensor B3. At this time, the timer 5 measures a propagation time TA from when the ultrasonic wave is transmitted until reception is detected.

  Next, the control unit 4 operates the direction switching circuit 8 to switch the propagation direction of the ultrasonic waves. That is, the drive circuit 6 is connected to the ultrasonic sensor B 3, and the reception output of the ultrasonic sensor A 2 is connected to the reception detection circuit 7. After that, the ultrasonic propagation time TB in the reverse direction is measured in the same manner as described above.

  When the flow velocity of the fluid to be measured is V, the crossing angle between the flow direction of the fluid to be measured and the propagation path of the ultrasonic wave is θ, and the distance between the two ultrasonic sensors is L, the flow velocity V can be obtained by the following equation. it can.

V = L / 2 · cos θ · (1 / TB-1 / TA)
Therefore, if the cross-sectional area of the flow path is S, the flow rate Q of the fluid to be measured is
Q = S · L / 2 · cos θ · (1 / TB-1 / TA)
It becomes.

Here, since the cross-sectional area S of the flow path, the crossing angle θ, and the distance L between the two ultrasonic sensors are known, assuming that the constant C = S · L / 2 · cos θ, Q = C · (1 / TA− 1 / TB) = C · (TB−TB) / TA · TB (Formula 1)
It can be expressed as.

  However, in reality, the path for measuring the propagation time TA in the circuit for measuring the propagation time is different from the path for measuring the propagation time TB, and there is a time difference. Since this time difference occurs as an error during flow rate measurement, a correction value in which TA and TB are the same when the flow rate is zero is stored in the storage means 9 and used for correction in order to eliminate this error.

  Then, the flow rate Q can be obtained by the following equation, where ΔT is the time difference caused by the path difference in the circuit.

  In the following equation, it is assumed that TB requires more time than TA due to a difference in circuit path. For TA in equation 1, ΔT / 2 is added, and ΔT / 2 is subtracted from TB. Is trying to eliminate.

  Q = C × [(TB−ΔT / 2) − (TA + ΔT / 2)] / [(TA + ΔT / 2) × (TB−ΔT / 2)]

Japanese Patent Laid-Open No. 11-304559

  However, since the correction value stored in the storage unit 9 is a constant in the conventional configuration, the circuit operation changes due to temperature, power supply voltage, aging, etc., and the time difference between different measurement paths varies. Correction could not be made and a measurement error occurred.

  The present invention solves the above-described conventional problems, and an object thereof is to provide an ultrasonic flowmeter with little error.

  In order to solve the conventional problem, an ultrasonic flowmeter of the present invention includes a flow path through which a fluid to be measured flows, an ultrasonic sensor A installed upstream of the flow path, and an ultrasonic sensor installed downstream. An acoustic wave sensor B, and a propagation time measuring means A for measuring an ultrasonic wave propagation time TA until the ultrasonic wave transmitted from the ultrasonic sensor A propagates through the measured fluid and is received by the ultrasonic sensor B; A propagation time measuring means B for measuring an ultrasonic propagation time TB until an ultrasonic wave transmitted from the ultrasonic sensor B propagates through the fluid to be measured and is received by the ultrasonic sensor A, and the propagation time. The measuring means A and the propagation time measuring means B are configured in the same semiconductor, the delay time measuring means for measuring the delay time of the semiconductor, the measurement time of the propagation time measuring means A and the propagation time measuring means B at the time of adjustment Time difference TdA The storage means for storing the semiconductor delay time TdB measured by the delay time measurement means, and the time difference TdA stored by the storage means is the time difference between the propagation time TA and the propagation time TB at the time of flow rate measurement. And calculating means for calculating the flow rate by correcting the delay time TdB and the delay time measured by the delay time measuring means, and correcting the correction value stored in the storage means by the output of the delay time measuring means Therefore, an appropriate correction value can be obtained even when the delay time of the circuit varies.

  The ultrasonic flowmeter of the present invention can measure an accurate flow rate by correcting a time difference due to a difference in circuit path in the propagation time measuring means with an appropriate correction value.

Whole block diagram in Embodiment 1 of this invention The block diagram which shows the connection of the propagation time measurement means A of this invention The block diagram which shows the connection of the propagation time measurement means B of this invention Circuit diagram showing circuit of delay time measuring means of the present invention Overall block diagram of a conventional ultrasonic flowmeter

The first invention is transmitted from the flow path through which the fluid to be measured flows, the ultrasonic sensor A installed upstream of the flow path, the ultrasonic sensor B installed downstream, and the ultrasonic sensor A. The propagation time measuring means A for measuring the propagation time TA of the ultrasonic wave until the ultrasonic wave propagates through the fluid to be measured and is received by the ultrasonic sensor B, and the ultrasonic wave transmitted from the ultrasonic sensor B Propagation time measuring means B that measures the propagation time TB of the ultrasonic wave that propagates through the fluid to be measured and is received by the ultrasonic sensor A, and the same semiconductor as the propagation time measuring means A and the propagation time measuring means B The delay time measuring means configured to measure the delay time of the semiconductor, the time difference TdA between the measurement times of the propagation time measuring means A and the propagation time measuring means B at the time of adjustment, and the delay time measuring means Half The storage means for storing the body delay time TdB, and the time difference between the propagation time TA and the propagation time TB at the time of measuring the flow, the time difference TdA, the delay time TdB and the delay time measurement means stored by the storage means. And calculating means for calculating the flow rate by correcting with the delay time measured in (1).

  The values stored in the storage means at the time of adjustment differ from the actual values due to the temperature and operating voltage of the propagation time measuring means A and B, and changes with time, but the value of the delay time measuring means also changes. Since the value stored in the storage means is corrected according to the amount and the deviation between the propagation time measurement means A and the propagation time measurement means B during actual operation is corrected, an accurate measurement result can be obtained.

  In the second invention, in particular, in the first invention, the delay time measuring means is constituted by a ring oscillator and an oscillation frequency measuring means, and when the delay time of the semiconductor is delayed, the oscillation frequency of the ring oscillator is delayed. . Then, by measuring the oscillation frequency by the oscillation frequency measuring means, the calculating means can obtain the delay time of the semiconductor by the amount of change of the oscillation frequency, and the delay time measuring means in the semiconductor with an easy configuration. Can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram showing the entire ultrasonic flowmeter according to the first embodiment of the present invention. As shown in the figure, the ultrasonic flowmeter of the present embodiment includes an ultrasonic sensor A2 installed on the upstream side of the flow path 1 through which the fluid to be measured flows, an ultrasonic sensor B3 installed on the downstream side, Propagation time measuring means A11 for measuring an ultrasonic wave propagation time TA until the ultrasonic wave transmitted from the ultrasonic sensor A2 propagates through the fluid to be measured that fills the flow path 1 and is received by the ultrasonic sensor B3; Conversely, the propagation time for measuring the ultrasonic propagation time TB until the ultrasonic wave transmitted from the ultrasonic sensor B3 propagates through the fluid to be measured filling the flow path 1 and is received by the ultrasonic sensor A2. The measurement means B12, the propagation time measurement means A11, and the propagation time measurement means B12 are configured in the same semiconductor 13 and have a delay time measurement means 14 for measuring the delay time of the semiconductor.

  In addition, the storage unit 15 that stores the time difference TdA between the propagation time measurement unit A11 and the propagation time measurement unit B12 and the delay time TdB of the semiconductor measured by the delay time measurement unit 14 during adjustment, and the actual flow rate measurement The time difference TdA ′ between the propagation time TA ′ and the propagation time TB ′ that are sometimes measured is the time difference TdA and delay time TdB that are stored in the storage unit 15 and the semiconductor delay time TdB that is measured by the delay time measurement unit 14. And calculating means 16 for calculating the flow rate by correcting with '.

  Here, at the time of adjustment, the flow rate is set to zero, and the time difference TdA between the propagation time TA and the propagation time TB measured by the propagation time measuring means A11 and the propagation time measuring means B12 is saved by the saving means 15 as a correction value. Further, the time difference TdA at this time is caused by a difference in the path between the propagation time measuring means A11 and the propagation time measuring means B12 in the semiconductor, and varies depending on time and temperature.

  2 and 3 are block diagrams showing differences in connection paths of the ultrasonic sensor A2, the ultrasonic sensor B3, the propagation time measuring means A11, and the propagation time measuring means B12 according to the first embodiment of the present invention. Hereinafter, the present embodiment will be described with reference to FIGS.

First, as shown in FIG. 2, the ultrasonic sensor A 2 is connected to the drive circuit 6 and the ultrasonic sensor B 3 is connected to the reception detection circuit 7 by the direction switching circuit 8. In this state, the control unit 4 starts the timer 5 and simultaneously operates the drive circuit 6. The ultrasonic wave transmitted from the ultrasonic sensor A2 driven by the drive circuit 6 propagates through the fluid to be measured in the flow path, is received by the ultrasonic sensor B3, and receives the output of the ultrasonic sensor B3. Reception is detected by the detection circuit 7. At this time, the timer 5 measures the forward propagation time TA from when the ultrasonic wave is transmitted until reception is detected.

  Next, as shown in FIG. 3, the control unit 4 operates the direction switching circuit 8 to switch the propagation direction of the ultrasonic waves. That is, the drive circuit 6 is connected to the ultrasonic sensor B 3, and the reception output of the ultrasonic sensor A 2 is connected to the reception detection circuit 7. Then, similarly to the measurement of the propagation time TA, the propagation time TB in the reverse direction is measured.

  Here, the time difference TdA stored in the storage unit 15 at the time of adjustment is deviated from the actual value due to the temperature, operating voltage, and temporal change of the propagation time measuring units A11 and B12. Similarly, the value of the delay time TdB of the semiconductor measured by the delay time measuring means 14 also changes. This change is caused by the propagation time measuring means A11, the propagation time measuring means B12, and the delay time measuring means 14 being all in the same semiconductor. Therefore, the increase / decrease value is correlated.

  Therefore, the time difference TdA ′ of the measurement time caused by the difference in the path between the propagation time measurement unit A11 and the propagation time measurement unit B12 during flow rate measurement can be obtained as TdA ′ = TdA × (TdB ′ / TdB).

  The calculating means 16 calculates the flow rate as a correction value by assuming that the obtained time difference TdA 'is caused by the path between the propagation time measuring means A11 and the propagation time measuring means B12 in actual measurement.

  As described above, an accurate flow rate can be measured by correcting the time difference due to the difference in the circuit path in the propagation time measuring means with the appropriate correction value.

  FIG. 4 is a circuit diagram showing the delay time measuring means 14 in the first embodiment of the present invention. The delay time measuring means 14 is composed of a ring oscillator 17 and a counter 18. The ring oscillator is configured in a ring shape by a NAND 19 and a plurality of inverters 20. The ring oscillator 17 oscillates while the input signal A is HI and is input to the NAND circuit, and the number of oscillations is counted by the counter 18.

  Here, the number of oscillations of the ring oscillator 17 within this time is counted by controlling the period during which the input signal A is Lo using a resonator that is not easily affected by voltage fluctuations or temperature changes. The number of oscillations is inversely proportional to the delay time. In this way, the delay time can be realized in the semiconductor with a simple circuit configuration.

  According to the ultrasonic flowmeter of the present invention, an accurate flow rate can be measured by correcting a time difference due to a difference in circuit path in the propagation time measuring means with an appropriate correction value.

1 Flow path 2 Ultrasonic sensor A
3 Ultrasonic sensor B
11 Propagation time measurement means A
12 Propagation time measurement means B
14 Delay time measurement means 15 Storage means 16 Calculation means

Claims (2)

A flow path through which the fluid to be measured flows;
An ultrasonic sensor A installed on the upstream side of the flow path and an ultrasonic sensor B installed on the downstream side;
A propagation time measuring means A for measuring an ultrasonic wave propagation time TA until an ultrasonic wave transmitted from the ultrasonic sensor A propagates through the fluid to be measured and is received by the ultrasonic sensor B;
A propagation time measuring means B for measuring an ultrasonic propagation time TB until the ultrasonic wave transmitted from the ultrasonic sensor B propagates through the fluid to be measured and is received by the ultrasonic sensor A;
The propagation time measuring means A and the propagation time measuring means B are configured in the same semiconductor, and the delay time measuring means for measuring the delay time of the semiconductor;
Storage means for storing a time difference TdA between the measurement times of the propagation time measurement means A and the propagation time measurement means B at the time of adjustment, and a semiconductor delay time TdB measured by the delay time measurement means;
The flow rate is corrected by correcting the time difference between the propagation time TA and the propagation time TB at the time of flow rate measurement with the time difference TdA, the delay time TdB, and the delay time measured by the delay time measurement unit. An ultrasonic flowmeter provided with a calculation means for calculating 2. The ultrasonic flowmeter according to claim 1, wherein the delay time measuring means comprises a ring oscillator and an oscillation frequency measuring means.

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